New Trend of Amperometric Gas Sensors Using Atomic Gold-Decorated Platinum/Polyaniline Composites

The Amperometric Gas Sensor (AGS) uses an electrode as the transducer element which converts its signal into a current from the electrochemical reaction of analytes taking place at the electrode surface. Many attempts to improve AGS performance, such as modifying the working electrode, applying a particular gas-permeable membrane, and selecting the proper electrolyte, etc., have been reported in the scientific literature. On the other hand, in the materials community, atomic gold has gained much attention because its physicochemical properties dramatically differ from those of gold nanoparticles. This paper provides an overview of the use of atomic gold in AGSs, both in a bulky AGS and a miniaturized AGS. In the miniaturized AGS, the system must be redesigned; for example, the aqueous electrolyte commonly used in a bulky AGS cannot be used due to volatility and fluidity issues. A Room Temperature Ionic Liquid (RTIL) can be used to replace the aqueous electrolyte since it has negligible vapor pressure; thus, a thin film of RTIL can be realized in a miniaturized AGS. In this paper, we also explain the possibility of using RTIL for a miniaturized AGS by incorporating a quartz crystal microbalance sensor. Several RTILs coated onto modified electrodes used for isomeric gas measurement are presented. Based on the results, the bulky and miniaturized AGS with atomic gold exhibited a higher sensor response than the AGS without atomic gold

Accelerometer time series augmentation through externally driving a non-linear dynamical system

These are experimental time series from an analog electronic circuit realizing a Rössler system, externally driven by physical recordings from an accelerometer monitoring the movements of cattle, taken from a pre-existing dataset (see below). They are provided to support the replication of the results reported in the associated publication, as well as any further public-domain academic research in the related fields, in compliance with the specified license terms and all applicable legal clauses. The following reference must be cited when using these data: Minati L, Li C, Bartels J, Chakraborty P, Li Z, Yoshimura N, Frasca M, Ito H, Accelerometer time series augmentation through externally driving a non-linear dynamical system, Chaos, Solitons and Fractals 168 (2023) 113100, DOI 10.1016/j.chaos.2023.113100. The present dataset only provides the analog electronic circuit outputs, and neither the accelerometer signals that were input to it nor the corresponding behavioral labels. Therefore, it cannot be used in isolation. Those essential elements need to be drawn from the following dataset: Ito H, Takeda K, Tokgoz KK, Minati L, Fukawa M, Li C, Bartels J, Rachi I, Sihan A, Japanese Black Beef Cow Behavior Classification Dataset, Available at https://zenodo.org/record/5849025. Usage is thus subject to citing and acknowledging this source, crediting its authors, abiding to its specific license terms and conditions, and citing the references indicated therein. See legend file for specifics, x10 up-sampling required. This work was supported in part by JSPS KAKENHI Grant Number 19H02191, and in part by JST-SPRING Grant Number JPMJSP2106. The authors are grateful to all the Research Institute for the Earth Inclusive Sensing members, and especially K. Takeda, K.K. Tokgoz, and M. Fukawa for their excellent support in establishing the publicly-available dataset used also in this study, and thank A. Tharayil Narayanan for useful discussions. L.M. developed the analog circuit and other concepts in collaboration with M.F. when based in Trento, Italy, later applying them to this study and performing the experiments and writing the manuscript while in Tokyo, Japan

Array of Miniaturized Amperometric Gas Sensors Using Atomic Gold Decorated Pt/PANI Electrodes in Room Temperature Ionic Liquid Films

Miniaturized sensors possess many advantages, such as rapid response, easy chip integration, a possible lower concentration of target compound detection, etc. However, a major issue reported is a low signal response. In this study, a catalyst, the atomic gold clusters of Aun where n = 2, was decorated at a platinum/polyaniline (Pt/PANI) working electrode to enhance the sensitivity of butanol isomers gas measurement. Isomer quantification is challenging because this compound has the same chemical formula and molar mass. Furthermore, to create a tiny sensor, a microliter of room-temperature ionic liquid was used as an electrolyte. The combination of the Au2 clusters decorated Pt/PANI and room temperature ionic liquid with several fixed electrochemical potentials was explored to obtain a high solubility of each analyte. According to the results, the presence of Au2 clusters increased the current density due to electrocatalytic activity compared to the electrode without Au2 clusters. In addition, the Au2 clusters on the modified electrode had a more linear concentration dependency trend than the modified electrode without atomic gold clusters. Finally, the separation among butanol isomers was enhanced using different combination of room-temperature ionic liquids and fixed potentials

Catalytic Activity of Atomic Gold-Decorated Polyaniline Support in Glucose Oxidation

Atomic-level gold clusters are decorated on a polyaniline (PANI) support by a cyclic atomic electrodeposition process, and the catalytic activity in the oxidation of glucose is studied. The evaluation is conducted by cyclic voltammetry using atomic-level gold clusters-decorated PANI (PANI/AuN, where N indicates the atomic size of the Au cluster and N = 1~3 in this study) as the working electrode and a solution containing 0 to 50.0 mM of glucose in phosphate-buffered saline. The catalytic activity is determined from the oxidation current observed at around +0.6 V vs. Ag/AgCl. The catalytic activity is found to be affected by the size of gold clusters decorated on the PANI/AuN, whereby the catalytic activity is low when N is 1 or 3. On the other hand, an obvious enhancement in the catalytic activity is observed for the PANI/Au2 electrode

Impurity analysis of electroplated gold components with multi-layered structures by thermal desorption spectrometry toward application in gold Micro electro mechanical system capacitive accelerometers

Au-based micro-electro-mechanical-system (Au-MEMS) capacitance accelerometers show high sensitivity by suppressing the mechanical noise because of the high mass density of gold (ρ = 19.3 g/cm3). On the other hand, their long-term reliability suffers from drift phenomena induced by the impurities incorporated in the key component during their fabrication process, such as the gold electroplating step. Herein, impurities in electroplated Au-based components for MEMS capacitive accelerometers are evaluated by thermal desorption spectrometry (TDS) measurements. The TDS measurement reveals that dominant desorption gases from the Au-based component are molecular hydrogen (H2) and water (H2O). These desorption gases are derived from impurities in the electroplated Au-based component, and the amount of these gases is significantly suppressed by a thermal treatment step. In conclusion, this study demonstrates that the electroplated Au-based component contains impurities originated from the fabrication process, and these impurities could be removed by a thermal treatment step